It is nowadays common to use a near-field magnetic coupling communication technology, such as NFC technology. This communication technology is able to be used for many applications, such as for example to pay contactlessly using for example a bank card or a mobile appliance such as a mobile telephone or a digital tablet. This technology may also be implemented in order to enable a user to access a vehicle and to start it using a mobile telephone, for example.
This technology has the advantage of enabling an identifier to be exchanged between for example a mobile telephone and a vehicle, at a secure distance, of the order of around ten centimeters, and therefore of enabling a vehicle to be either unlocked or started in complete security.
It is therefore known to equip a vehicle with NFC hands-free access means, either for unlocking or for starting said vehicle.
To this end, the vehicle generally comprises, for unlocking those components of the vehicle that open, a first NFC antenna, directed toward the outside of the vehicle, for example situated in a door handle, and a first NFC reader, linked to a microcontroller and for starting the engine of the vehicle, a second NFC antenna, situated inside the vehicle, for example, in the dashboard, and a second NFC reader, linked to a second microcontroller or to the same microcontroller.
In other words, the vehicle comprises two identical NFC detection systems (NFC antenna, NFC reader and microcontroller) at two separate locations on the vehicle, each dedicated to one action: unlocking or starting the vehicle.
It will be understood, for reasons of cost and of ergonomics, that it would be desirable to group together these two NFC detection systems into a single one, situated in a single position on the vehicle, able to be accessed from the outside and from the inside, for example either in the driver's door of the vehicle, or in a window pane of said door, so as to detect the approach of the user's apparatus, whether it be situated outside or inside the vehicle, so as to trigger the corresponding action, i.e. unlocking or starting.
The NFC bidirectional detection device D from the prior art is illustrated in FIG. 1.
A first NFC antenna A1 is directed toward the outside EXT of the vehicle and a second NFC antenna A2 is directed toward the inside INT of the vehicle, said two antennae A1, A2 are situated opposite one another, separated by two layers of ferrites F1, F2, which layers are themselves spaced apart by a copper layer C situated on a printed circuit board 10.
NFC antenna is understood here to mean an RFID (acronym for ‘radiofrequency identification’) tag.
The proximity of the two NFC antennae creates interference and requires the presence of two additional ferrites F1, F2 (as illustrated in FIG. 1) that are separated by a conductive copper layer C.
The copper layer C makes it possible to dissipate the few electromagnetic currents that manage to pass through the ferrites F1, F2; specifically, said ferrites do not provide perfect shielding of the electromagnetic waves received by the NFC antennae A1 and A2. A small number of the electromagnetic waves received by the first or by the second NFC antenna A1, A2 pass through the first ferrite F1 or the second ferrite F2 and then disturb the other of said two NFC antennae A1, A2. The copper layer C has the advantage of dissipating these electromagnetic waves, thus preventing them from disturbing the other NFC antenna A1, A2.
Each NFC antenna, the first NFC antenna A1 and the second NFC antenna A2, is linked to a dedicated NFC reader, respectively to a first NFC reader 21 and to a second NFC reader 22, both connected to a microcontroller 20.
This bidirectional detection device D from the prior art has the drawbacks of being expensive (two ferrites F1, F2, two NFC readers 21, 22 and a copper layer C) and, due to the proximity between the first NFC antenna and the second NFC antenna A1, A2, of substantially impairing their performance, in spite of the presence of the two ferrites F1, F2 and of the additional copper layer C.